One of the new Covid-19 cases from Auckland travelled to Rotorua while she was symptomatic, Dr Ashley Bloomfield said today.
The woman in her twenties travelled to Rotorua on Saturday.
"We are working with urgency to find out which places the family visited," the Director-General of Health said.
The family are still in isolation at home and authorities are looking into whether they should go into quarantine facilities.
"We are taking a rapid response," Prime Minister Jacinda Ardern said, adding that was through contact tracing, information gathering and mass testing.
All aged care facilities will close their doors from noon today (except for staff).
Ms Ardern said they were looking for potential casual contacts in Rotorua and looking for the source in Auckland.
"Testing will play an important role," she said, with new testing stations opening across the city.
Ms Ardern said she had a special request that only people with symptoms or with links to the workplaces of the new Auckland cases get tested.
"If you have symptoms or if a medical professional or healthline (say you should), please get tested."
It comes as Auckland is set to move to Alert Level 3 and the rest of the country to Alert Level 2 at noon today until midnight Friday.
It was spurred by four new Covid-19 cases from a South Auckland family acquired through community transmission.
1 NEWS also understands the dissolution of Parliament has been delayed following this latest Covid-19 outbreak.
New Zealand’s 52nd Parliament was due to be dissolved this morning but there’s been calls to delay that.